The ATP synthase from mitochondria of animal cells is an important enzyme which couples proton translocation to ATP synthesis, to provide chemical energy needed for many biological processes. It consists of F1 (a soluble domain with 5 subunit types of a total mass of 370 kD), a stalk and F0 (a membrane domain with at least three subunit types). The x ray crystallographic structure for the F1 has been determined to 2.8 [unreadable] but the structure of the rest of the molecule is still unknown. We have carried out preliminary experiments to image the entire enzyme with the hope that we can define the overall organization of the three components of this large enzyme.